kinda stuck in a 3 way...?

no don't tell her she will have to find out on her own or from someone else. that will backfire horribly. know from experience. i told a girl stuff her bf did behind her back and all i got was a hug thank you your a great friend and that was 3 months ago. we never got close to a relationship in fact it put me in the friend zone ever more when that was already where i was at.. :/ anyway id keep the feelings to yourself till they break up because if she's really in love with him the way you say it wont matter to her. your best bet i know this wont be easy. but its to let her go and to stop being as good of friends with her and then when they break up which will probably be hard on her. so wait for a few months after that so your not the rebound and make your move. that's honestly probably your best bet at getting her. and you wont loose a best friend over it or get you *** kicked either.

This happens to so many people. Instead of telling her what a bad person he is, ask first if she knows anything that he's done behind her back. If she doesn't know, then maybe you should tell her. (Don't do this to try to break them up though, bad bad bad.) But be prepared to have a broken hearted or very angry girl on your hands. More then likely if the current boyfriend finds out, you three will have some problems. And about your second question, it's never really a good thing to tell a girl how you feel when they have a boyfriend. It makes everything so complicated. Have you tried giving her hints about how you feel? If not, you should try that. Best of luck to you.

Well, I know if I was her I would want to know.

I think whether you should tell her or not depends on her personality.

It sounds like she really likes her boyfriend so she'll probably be pretty upset when she finds out.

She might be better off just finding out on her own.

Do what you think will be best, but keep her feelings in mind.